Beam.update_filling_pattern and Beam.update_distance_between_bunches are now called directly in the __init__ when a bunch_list is given.
Beam.init_bunch_list_mpi is a convenience method to initialize a beam using MPI parallelisation with a Bunch per core.
Add tests for Beam.init_bunch_list_mpi

**Warning, this fix contains changes which will change the default behavior of core functions:**

* Default behavior of Optics is changed when AT lattice is loaded: now default to optic function to s=0 instead of average ones.
* Default behavior of LongRangeResistiveWall and ImpedanceModel when an AT lattice is loaded is to normalized by average_beta / local_beta
* Adds Optics.average_beta attribute
* Add pytest markers for tests and update .gitlab-ci.yml and pyproject.toml files.

Code modifications:

* [Fix] adts in TransverseMapSector
* ComplexData.name_and_coefficients_table is now a staticmethod.
* Extend WakeField to "mixed" componenets (xydip, yxdip, ...).
* Small fix/improvements for rf.py (CavityResonator for n_bin=1)
* [Fix] WakePotential.check_sampling method.
* [Fix] Sweep.plot method.
* Add Element.track_bunch_if_non_empty decorator.
* Modify Bunch.binning to add a return_full_length optional parameter.
* Modify Mpi.share_distributions for n_bin=1.
* Modify TransverseSpaceCharge to work with track_alive = True.
* Modify WakePotential for n_bin=1 and use track_bunch_if_non_empty decorator.
* [Fix] IntrabeamScattering for nonuniform fills with Beam.mpi_switch == False
* Modify PhysicalModel to return errors if needed.
* Update BeamIonElement

Project management:

* Update pyproject.toml and poetry.lock with pytest-mock
* Add assert_attr_changed test function.